lib/tevent/tevent_select.c

   1 /*
   2    Unix SMB/CIFS implementation.
   3    main select loop and event handling
   4    Copyright (C) Andrew Tridgell        2003-2005
   5    Copyright (C) Stefan Metzmacher      2005-2009
   6
   7      ** NOTE! The following LGPL license applies to the tevent
   8      ** library. This does NOT imply that all of Samba is released
   9      ** under the LGPL
  10
  11    This library is free software; you can redistribute it and/or
  12    modify it under the terms of the GNU Lesser General Public
  13    License as published by the Free Software Foundation; either
  14    version 3 of the License, or (at your option) any later version.
  15
  16    This library is distributed in the hope that it will be useful,
  17    but WITHOUT ANY WARRANTY; without even the implied warranty of
  18    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  19    Lesser General Public License for more details.
  20
  21    You should have received a copy of the GNU Lesser General Public
  22    License along with this library; if not, see <http://www.gnu.org/licenses/>.
  23 */
  24
  25 #include "replace.h"
  26 #include "system/filesys.h"
  27 #include "system/select.h"
  28 #include "tevent.h"
  29 #include "tevent_util.h"
  30 #include "tevent_internal.h"
  31
  32 struct select_event_context {
  33         /* a pointer back to the generic event_context */
  34         struct tevent_context *ev;
  35
  36         /* the maximum file descriptor number in fd_events */
  37         int maxfd;
  38
  39         /* information for exiting from the event loop */
  40         int exit_code;
  41 };
  42
  43 /*
  44   create a select_event_context structure.
  45 */
  46 static int select_event_context_init(struct tevent_context *ev)
  47 {
  48         struct select_event_context *select_ev;
  49
  50         select_ev = talloc_zero(ev, struct select_event_context);
  51         if (!select_ev) return -1;
  52         select_ev->ev = ev;
  53
  54         ev->additional_data = select_ev;
  55         return 0;
  56 }
  57
  58 /*
  59   recalculate the maxfd
  60 */
  61 static void calc_maxfd(struct select_event_context *select_ev)
  62 {
  63         struct tevent_fd *fde;
  64
  65         select_ev->maxfd = 0;
  66         for (fde = select_ev->ev->fd_events; fde; fde = fde->next) {
  67                 if (fde->fd > select_ev->maxfd) {
  68                         select_ev->maxfd = fde->fd;
  69                 }
  70         }
  71 }
  72
  73
  74 /* to mark the ev->maxfd invalid
  75  * this means we need to recalculate it
  76  */
  77 #define EVENT_INVALID_MAXFD (-1)
  78
  79 /*
  80   destroy an fd_event
  81 */
  82 static int select_event_fd_destructor(struct tevent_fd *fde)
  83 {
  84         struct tevent_context *ev = fde->event_ctx;
  85         struct select_event_context *select_ev = NULL;
  86
  87         if (ev) {
  88                 select_ev = talloc_get_type(ev->additional_data,
  89                                             struct select_event_context);
  90
  91                 if (select_ev->maxfd == fde->fd) {
  92                         select_ev->maxfd = EVENT_INVALID_MAXFD;
  93                 }
  94         }
  95
  96         return tevent_common_fd_destructor(fde);
  97 }
  98
  99 /*
 100   add a fd based event
 101   return NULL on failure (memory allocation error)
 102 */
 103 static struct tevent_fd *select_event_add_fd(struct tevent_context *ev, TALLOC_CTX *mem_ctx,
 104                                              int fd, uint16_t flags,
 105                                              tevent_fd_handler_t handler,
 106                                              void *private_data,
 107                                              const char *handler_name,
 108                                              const char *location)
 109 {
 110         struct select_event_context *select_ev = talloc_get_type(ev->additional_data,
 111                                                            struct select_event_context);
 112         struct tevent_fd *fde;
 113
 114         if (fd < 0 || fd >= FD_SETSIZE) {
 115                 errno = EBADF;
 116                 return NULL;
 117         }
 118
 119         fde = tevent_common_add_fd(ev, mem_ctx, fd, flags,
 120                                    handler, private_data,
 121                                    handler_name, location);
 122         if (!fde) return NULL;
 123
 124         if ((select_ev->maxfd != EVENT_INVALID_MAXFD)
 125             && (fde->fd > select_ev->maxfd)) {
 126                 select_ev->maxfd = fde->fd;
 127         }
 128         talloc_set_destructor(fde, select_event_fd_destructor);
 129
 130         return fde;
 131 }
 132
 133 /*
 134   event loop handling using select()
 135 */
 136 static int select_event_loop_select(struct select_event_context *select_ev, struct timeval *tvalp)
 137 {
 138         fd_set r_fds, w_fds;
 139         struct tevent_fd *fde;
 140         int selrtn;
 141
 142         /* we maybe need to recalculate the maxfd */
 143         if (select_ev->maxfd == EVENT_INVALID_MAXFD) {
 144                 calc_maxfd(select_ev);
 145         }
 146
 147         FD_ZERO(&r_fds);
 148         FD_ZERO(&w_fds);
 149
 150         /* setup any fd events */
 151         for (fde = select_ev->ev->fd_events; fde; fde = fde->next) {
 152                 if (fde->fd < 0 || fde->fd >= FD_SETSIZE) {
 153                         errno = EBADF;
 154                         return -1;
 155                 }
 156
 157                 if (fde->flags & TEVENT_FD_READ) {
 158                         FD_SET(fde->fd, &r_fds);
 159                 }
 160                 if (fde->flags & TEVENT_FD_WRITE) {
 161                         FD_SET(fde->fd, &w_fds);
 162                 }
 163         }
 164
 165         if (select_ev->ev->signal_events &&
 166             tevent_common_check_signal(select_ev->ev)) {
 167                 return 0;
 168         }
 169
 170         selrtn = select(select_ev->maxfd+1, &r_fds, &w_fds, NULL, tvalp);
 171
 172         if (selrtn == -1 && errno == EINTR &&
 173             select_ev->ev->signal_events) {
 174                 tevent_common_check_signal(select_ev->ev);
 175                 return 0;
 176         }
 177
 178         if (selrtn == -1 && errno == EBADF) {
 179                 /* the socket is dead! this should never
 180                    happen as the socket should have first been
 181                    made readable and that should have removed
 182                    the event, so this must be a bug. This is a
 183                    fatal error. */
 184                 tevent_debug(select_ev->ev, TEVENT_DEBUG_FATAL,
 185                              "ERROR: EBADF on select_event_loop_once\n");
 186                 select_ev->exit_code = EBADF;
 187                 return -1;
 188         }
 189
 190         if (selrtn == 0 && tvalp) {
 191                 /* we don't care about a possible delay here */
 192                 tevent_common_loop_timer_delay(select_ev->ev);
 193                 return 0;
 194         }
 195
 196         if (selrtn > 0) {
 197                 /* at least one file descriptor is ready - check
 198                    which ones and call the handler, being careful to allow
 199                    the handler to remove itself when called */
 200                 for (fde = select_ev->ev->fd_events; fde; fde = fde->next) {
 201                         uint16_t flags = 0;
 202
 203                         if (FD_ISSET(fde->fd, &r_fds)) flags |= TEVENT_FD_READ;
 204                         if (FD_ISSET(fde->fd, &w_fds)) flags |= TEVENT_FD_WRITE;
 205                         if (flags) {
 206                                 fde->handler(select_ev->ev, fde, flags, fde->private_data);
 207                                 break;
 208                         }
 209                 }
 210         }
 211
 212         return 0;
 213 }
 214
 215 /*
 216   do a single event loop using the events defined in ev
 217 */
 218 static int select_event_loop_once(struct tevent_context *ev, const char *location)
 219 {
 220         struct select_event_context *select_ev = talloc_get_type(ev->additional_data,
 221                                                            struct select_event_context);
 222         struct timeval tval;
 223
 224         if (ev->signal_events &&
 225             tevent_common_check_signal(ev)) {
 226                 return 0;
 227         }
 228
 229         if (ev->immediate_events &&
 230             tevent_common_loop_immediate(ev)) {
 231                 return 0;
 232         }
 233
 234         tval = tevent_common_loop_timer_delay(ev);
 235         if (tevent_timeval_is_zero(&tval)) {
 236                 return 0;
 237         }
 238
 239         return select_event_loop_select(select_ev, &tval);
 240 }
 241
 242 static const struct tevent_ops select_event_ops = {
 243         .context_init           = select_event_context_init,
 244         .add_fd                 = select_event_add_fd,
 245         .set_fd_close_fn        = tevent_common_fd_set_close_fn,
 246         .get_fd_flags           = tevent_common_fd_get_flags,
 247         .set_fd_flags           = tevent_common_fd_set_flags,
 248         .add_timer              = tevent_common_add_timer,
 249         .schedule_immediate     = tevent_common_schedule_immediate,
 250         .add_signal             = tevent_common_add_signal,
 251         .loop_once              = select_event_loop_once,
 252         .loop_wait              = tevent_common_loop_wait,
 253 };
 254
 255 _PRIVATE_ bool tevent_select_init(void)
 256 {
 257         return tevent_register_backend("select", &select_event_ops);
 258 }